1. Field of the Invention
The present invention relates generally to fluid discharge nozzles, and in particular to a fire fighting tool for producing a swirling (rotating) fog pattern that has a forward thrust component.
2. Description of the Related Art
Spray discharge nozzles have many applications, and fire fighting is one of particular interest. It is well known that water absorbs not only heat but also many of the toxic gases of a fire and tends to clear away the smoke and does so most effectively when broken up into a fine spray or mist. Spray generating nozzles distribute the water discharge over a larger volume than do conventional fluid discharge nozzles in which water is discharged in a converging pattern of diffused solid streams. Spray generating nozzles are particularly useful in combating interior fires and are often used to provide protection for firefighting personnel by creating a water spray shield around the firefighters.
Conventional spray generating nozzles typically include a housing, a passageway for conducting water from a water supply source such as a fire hose from the inlet to the discharge end of the nozzle and a device for particulating the water to break it up into a fine stream. Multiple openings intersect the discharge end of the nozzle for directly diffusing the discharge spray outwardly from the nozzle. A commonly used device for particulating water is an internal impeller, which turns in response to the flow of water across obliquely inclined impeller surfaces inside the housing.
One limitation of conventional spray generating nozzles is that a high pressure source of water must be available to provide sufficient projection for the discharge spray. Because the discharge nozzle outlet is substantially smaller than the supply hose in order to produce a diffused spray, a back pressure builds up within the nozzle housing, thereby limiting the discharge flow rate. The use of an internal impeller to particulate the water also requires mechanical bearings and the like, which increases the cost and mechanical complexity of the nozzle.
U.S. Pat. No. 5,351,891 to Hansen and others show a fixed, non-rotatable spray head in which discharge orifices project a focused, converging jet spray discharge pattern.
The nozzle disclosed in U.S. Pat. No. 4,697,740 to Ivy is a substantial improvement over conventional spray nozzles by virtue of its ability to generate a large cloud of fog or fine mist that is particularly effective for smothering a blaze. This is made possible by a rotary nozzle in which the discharge orifices project water droplets radially outwardly thereby producing a static fog pattern. Because the cloud remains static or centered relative to the nozzle, it is necessary for fire fighting personnel to position the rotary nozzle in close proximity to the blaze in order for it to have effective coverage. Moreover, by placing the nozzle close to the fire source, the mist cloud becomes caught in the updraft and is pulled away from the fire. Because the static cloud is not controllable in direction, it is necessary for the nozzle to be attended by an observer so that it can be repositioned from time to time to maintain the protective thermal shield around the fire source.
A limitation of conventional fog-cloud or mist-cloud generator nozzles is that the movement of the fog cloud or mist pattern is not controllable in any particular direction, and tends to remain centered on the nozzle or to drift randomly. It is often necessary for fire fighter personnel to approach dangerously close to a very hot fire in order to establish a mist cloud and hold it centered on the fire, to establish a thermal shield that allows the fire fighting personnel to work safely, and to smother the fire until it is extinguished or brought under control. This exposes the fire fighters to risk of serious burn injury and smoke inhalation, particularly where chemical fuel source fires are involved.
For these reasons, there is a continuing interest in improving fire fighting equipment generally, and water spray projection equipment in particular, especially for use around intense blaze situations. Improvements are needed in water projection equipment that will extend the safe operational limits of standard protective clothing and respiration equipment, and allow fire fighting personnel to work safely and effectively in close proximity to a fire source.